Abstract

A structural analysis of the base metal sulfide deposits at the Heath Steele mines, northern New Brunswick, is presented. The structural similarity of the deposits is defined and their relationships to one another discussed.The deposits are spatially associated with Ordovician sedimentary rocks, which are situated in an igneous rock complex comprising felsic and basic volcanics, volcaniclastics, and intrusives. The complex has been subjected to low-grade metamorphism and five generations of deformation (D 1 -D 5 ). The first two generations of deformation (D 1 and D 2 ) are represented by transposition foliations (S 1 and S 2 ). The present attitude of the S 2 foliation is a result of recumbent folding (D 3 ) and two generations of open folds with vertical axial planar cleavages striking northwest (S 4 foliation) and northeast (S 5 foliation). The S 1 foliation is axial planar to conical F 1 folds. Regionally, such folds have been associated with thrusting (D 1 ) along the earliest recognized layering (S 0 foliation). Vein swarms illustrate the local importance of solute mass transfer during this event, at the Heath Steele mines culminating in fracture-controlled alteration along a brittle-ductile deformation (D 1 ) shear zone near the sulfide deposits, and development of metasomatic breccia in the sulfide deposits.Overall, the deposits occur along the S 0 foliation, the contact between augen schists and the metasedimentary rocks, but massive sulfides are concentrated in F 1 fold closures, forming pods and slabs parallel to the S 1 foliation. This concentration reflects either mobilization of preexisting sulfides (during D 1 ) or deposit formation by mineralization during D 1 . If the contact (in S 0 ) is nontectonic, a stratigraphic control on the location of the deposits is indicated and their association with iron-formation argues for a syngenetic origin. Conclusive evidence for these models has been obliterated by the intense deformation and solution transfer.

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